Surface mounted components (SMCs) are placed on printed wiring boards (PWBs) and hybrid micro-circuits (HMCs) by assembly machines that automatically pick the components out of a component feeder and place the components in a desired place on the PWB or HMC. The machines have a machine head that must move accurately with respect to both X, Y and rotational axes in order to properly perform its pick and place tasks.
In accordance with conventional approaches, a laser device is normally used to check positional accuracy of automated placement machinery. However, setup procedures for laser devices are complicated and time consuming. As a result, placement machines cannot be checked routinely for axis positioning inaccuracies. Another disadvantage with checking positional accuracy with a laser is that the laser is used to check the position of machine placement head only. A direct measurement of the positional accuracy of the placed component is not made, thus mechanical inaccuracies occurred during the actual component placement are not measured by the laser system. The net result is that the improperly assembled product itself becomes the indicator that something is wrong with an assembly machine.
The following patents are indicative of the state-of-the-art as revealed in the patent literature: U.S. Pat. Nos. 3,548,493 to Hubbard; 3,621,554 to Feldman et al.; 3,859,723 to Hamer et al.; 3,982,979 to Hentz et al., and 4,403,406 to Foley. Generally, these patents are directed to manufacturing tools for aiding in the assembly of electrical components on a substrate. The patents to Hubbard, Feldman et al. and Foley disclose box-like structures with specialized lighting which assists the operator in locating the correct area on the substrate corresponding to the component to be placed. The lighting systems of Hubbard and Foley also provide methods for assisting an operator in placing components in proper orientation, while the patents to Hamer et al. and Hentz et al. are manufacturing tools which aid an assembler in manually placing small devices (typically less than 0.040") on an electrical substrate. None of the patents solve the problem of evaluating the accuracy of a placement machine prior to actual use of the placement machine so that the placement machine can be properly programmed for a manufacturing run.